Table 2 Overview of the GRADE system for grading the quality of evidence: criteria for assigning grade of evidence
Criteria for assigning level of evidence | |
|---|---|
Type of evidence | |
Randomized trial | High |
Observational study | Low |
Any other type of research evidence | Very low |
Increase level if: | |
Strong association | (+1) |
Very strong association | (+2) |
Evidence of a dose response gradient | (+1) |
Plausible confounders reduced the observed effect | (+1) |
Decrease level if: | |
Serious or very serious limitations to study quality | (-1) or (-2) |
Important inconsistency | (-1) |
Some or major uncertainty about directness | (-1) or (-2) |
Imprecise or sparse dataa | (-1) |
High probability of reporting bias | (-1) |